Synthesis and antitumor activities of 1,2,3-triazines and their benzo- and heterofused derivatives

Tandem diazotization/cyclization approach for the synthesis of a fused 1,2,3-triazinone-furazan/furoxan heterocyclic system

A straightforward protocol for the synthesis of a previously unknown [1,2,5]oxadiazolo[3,4-d][1,2,3]triazin-7(6H)-one heterocyclic system was developed. The described approach is based on tandem diazotization/azo coupling reactions of (1,2,5-oxadiazolyl)carboxamide derivatives bearing both aromatic and aliphatic substituents. The NO-donor ability of the synthesized furoxano[3,4-d][1,2,3]triazin-7(6H)-ones was additionally evaluated. The elaborated method provides access to novel nitrogen heterocyclic compounds with potential applications as drug candidates or thermostable components of functional organic materials.

Solid Phase Synthesis, DFT Calculations, Molecular Docking, and Biological Studies of Symmetrical N 2,N 4,N 6-Trisubstituted-1,3,5-triazines

A diversity-oriented, multicomponent convergent synthesis of symmetrical triazines through a one-pot protocol is presented in this research project. The assembly of trisubstituted triazines was initially carried out using easily available reagents through three different protocols, i.e., conventional, MW-assisted synthesis, and solid-supported MW-assisted synthesis using organic and inorganic support to carry out a comparative analysis as to which procedure best corresponds to a greener synthesis protocol. The compounds formed were characterized for structure elucidation and subjected to in vitro anticancer and antibacterial screening. Additionally, computational studies, such as DFT calculations and molecular docking analyses, were conducted.

Denitrogenative dismantling of heteroaromatics by nucleophilic substitution reactions with diazomethyl compounds

Nucleophiles from deprotonation of diazomethyl compounds having diverse electron withdrawing groups react with 4-carboxylato-1,2,3-triazines at the 6-position to extrude dinitrogen and produce diazovinylketoesters compounds with five or six linear contiguous sp2-hybridized carbons, whereas these same nucleophiles react with 4-carboxylato-1,2,3-triazine 1-oxides, also at the 6-position, to form pyrazolines with the expulsion of nitrous oxide and cyanocarboxylate. This disparity is due to the significant difference in reactivity of the nucleophilic addition products.

Diazotization of o-Aminoamidoximes for the Preparation of Energetic 6,5,6-Fused 1,2,3-Triazine-3-oxides

Two 6,5,6-fused 1,2,3-triazine-3-oxides (4 and 6) were designed and synthesized via the reaction of o-aminoamidoximes with sodium nitrite. In addition, the ring-opening products (5, 7, and 8) derived from 1,2,3-triazine-3-oxides were isolated and characterized. A comprehensive exploration of the reaction mechanism governing the ring-opening process was performed through a combination of theoretical and experimental studies. Notably, compound 4 exhibited commendable detonation properties and low sensitivity, demonstrating its promising potential as an energetic material.

Synthesis and Psychotropic Properties of Novel Condensed Triazines for Drug Discovery

The exploration of heterocyclic compounds and their fused analogs, featuring key pharmacophore fragments like pyridine, thiophene, pyrimidine, and triazine rings, is pivotal in medicinal chemistry. These compounds possess a wide array of biological activities, making them an intriguing area of study. The quest for new neurotropic drugs among derivatives of these heterocycles with pharmacophore groups remains a significant research challenge. The aim of this research work was to develop a synthesis method for new heterocyclic compounds, evaluate their neurotropic and neuroprotective activities, study histological changes, and perform docking analysis. Classical organic synthesis methods were used in the creation of novel heterocyclic systems containing pharmacophore rings. To evaluate the neurotropic activity of these synthesized compounds, a range of biological assays were employed. Docking analysis was conducted using various software packages and methodologies. The neuroprotective activity of compound 13 was tested in seizures with and without pentylenetetrazole (PTZ) administration. Histopathological examinations were performed in different experimental groups in the hippocampus and the entorhinal cortex. As a result of chemical reactions, 16 new, tetra- and pentacyclic heterocyclic compounds were obtained. The biologically studied compounds exhibited protection against PTZ seizures as well as some psychotropic effects. The biological assays evidenced that 13 of the 16 studied compounds showed a high anticonvulsant activity by antagonism with PTZ. The toxicity of the compounds was low. According to the results of the study of psychotropic activity, it was found that the selected compounds have a sedative effect, except compound 13, which exhibited activating behavior and antianxiety effects (especially compound 13). The studied compounds exhibited antidepressant effects, especially compound 13, which is similar to diazepam. Histopathological examination showed that compound 13 produced moderate changes in the brain and exhibited neuroprotective effects in the entorhinal cortex against PTZ-induced damage, reducing gliosis and neuronal loss. Docking studies revealed that out of 16 compounds, 3 compounds bound to the γ-aminobutyric acid type A (GABAA) receptor. Thus, the selected compounds demonstrated anticonvulsant, sedative, and activating behavior, and at the same time exhibited antianxiety and antidepressant effects. Compound 13 bound to the GABAA receptor and exhibited antianxiety, antidepressant, and neuroprotective effects in the entorhinal cortex against PTZ-induced changes.

Site Reversal in Nucleophilic Addition to 1,2,3-Triazine 1-Oxides

One of the most important reactions of 1,2,3-triazines with a dienophile is inverse electron demand Diels-Alder (IEDDA) cycloaddition, which occurs through nucleophilic addition to the triazine followed by N2 loss and cyclization to generate a heterocycle. The site of addition is either at the 4- or 6-position of the symmetrically substituted triazine core. Although specific examples of the addition of nucleophiles to triazines are known, a comprehensive understanding has not been reported, and the preferred site for nucleophilic addition is unknown and unexplored. With access to unsymmetrical 1,2,3-triazine-1-oxides and their deoxygenated 1,2,3-triazine compounds, we report C-, N-, H-, O-, and S-nucleophilic additions on 1,2,3-triazine and 1,2,3-triazine-1-oxide frameworks where the 4- and 6-positions could be differentiated. In the IEDDA cycloadditions using C- and N-nucleophiles, the site of addition is at C-6 for both heterocyclic systems, but product formation with 1,2,3-triazine-1-oxides is faster. Other N-nucleophile reactions with triazine 1-oxides show addition at either the 4- or 6-position of the triazine 1-oxide ring, but nucleophilic attack only occurs at the 6-position on the triazine. Hydride from NaBH4 undergoes addition at the 6-position on the triazine and the triazine 1-oxide core. Alkoxides show a high nucleophilic selectivity for the 4-position of the triazine 1-oxide. Thiophenoxide, cysteine, and glutathione undergo nucleophilic addition on the triazine core at the 6-position, while addition occurs at the 4-position of the triazine 1-oxide. These nucleophilic additions proceed under mild reaction conditions and show high functional group tolerance. Computational studies clarified the roles of the nucleophilic addition and nitrogen extrusion steps and the influence of steric and electronic factors in determining the outcomes of the reactions with different nucleophiles.

An efficient one pot synthesis of (2-hydroxyphenyl)-5-phenyl-6-(pyrrolidine-1-carbonyl)-1H-pyrano[2,3-d]pyrimidine-2,4(3H,5H)-dione derivatives as a potent biological agents

In this paper, we reported the synthesis of a novel series of (2-hydroxyphenyl)-5-phenyl-6-(pyrrolidine-1-carbonyl)-1H-pyrano[2,3-d]pyrimidine-2,4(3H,5H)-dione derivatives 5(a-j) by the reaction of 4-hydroxy coumarin, substituted aldehydes, barbituric acid, and pyrolidine in ethanol at ambient temperature. The titled pyranopyrimidines 5(a-j) were characterized by spectral analysis including IR, NMR (¹H & ¹³C), and HRMS. The newly synthesized compounds were examined for in vitro anti-inflammatory activity. The results demonstrated that compound 5b displayed excellent efficacy and the remaining compounds exhibited moderate activity. Also, the potency of the new compounds toward antimicrobial and antifungal activity was investigated by a disk diffusion method. The results show that compounds 5b and 5g were more potent than the other compounds. Furthermore, the molecular docking studies were carried out using a COX-2 receptor.

Cross-Coupling Reactions of 5-Bromo-1,2,3-triazine

An efficient Pd catalyzed cross-coupling method for 5-bromo-1,2,3-triazine is described. Optimization of the reaction conditions allowed for the preparation of a representative scope of (hetero)aryl-1,2,3-triazines (20 examples, up to 97% yield). The reaction scope was evaluated using a data science enabled boronic acid chemical space to assess the generality of the method. Additionally, diversification of the resulting products enabled the preparation of pyrimidines and pyridines in yields of up to 80% and in only two steps.

Synthesis of 1,2,3-Triazine Derivatives by Deoxygenation of 1,2,3-Triazine 1-Oxides

A convenient, efficient, and inexpensive method has been developed for the synthesis of 1,2,3-triazine derivatives via deoxygenation of 1,2,3-triazine 1-oxide using trialkyl phosphites. Triethyl phosphite is more reactive than trimethyl phosphite, and both phosphites form their corresponding phosphates in these reactions. This procedure provides a range of aromatic and aliphatic substituted 1,2,3-triazine-4-carboxylate derivatives cleanly in high yields. Unexpected 1,2,4-triazine derivatives were also obtained as minor products during deoxygenation of 1,2,3-triazine-4-carboxylate 1-oxides having an aliphatic substituent at the 5-position.

Triazines: Syntheses and Inverse Electron-demand Diels-Alder Reactions

Triazines are an important class of six-membered aromatic heterocycles possessing three nitrogen atoms, resulting in three types of regio-isomers: 1,2,4-triazines (a-triazines), 1,2,3-triazines (v-triazines), and 1,3,5-triazines (s-triazines). Notably, the application of triazines as cyclic aza-dienes in inverse electron-demand Diels-Alder (IEDDA) cycloaddition reactions has been established as a unique and powerful method in N-heterocycle synthesis, natural product preparation, and bioorthogonal chemistry. In this review, we comprehensively summarize the advances in the construction of these triazines via annulation and ring-expansion reactions, especially emphasizing recent developments and challenges. The synthetic transformations of triazines are focused on IEDDA cycloaddition reactions, which have allowed access to a wide scope of heterocycles, including pyridines, carbolines, azepines, pyridazines, pyrazines, and pyrimidines. The utilization of triazine IEDDA reactions as key steps in natural product synthesis is also discussed. More importantly, a particular attention is paid on the bioorthogonal application of triazines in fast click ligation with various strained alkenes and alkynes, which opens a new opportunity for studying biomolecules in chemical biology.

Intermolecular [5 + 1]-Cycloaddition between Vinyl Diazo Compounds and tert-Butyl Nitrite to 1,2,3-Triazine 1-Oxides and Their Further Transformation to Isoxazoles

1,2,3-Triazine 1-oxides are formed by nitrosyl addition from tert-butyl nitrite to the vinylogous position of vinyl diazo compounds. This transformation, which is a formal intermolecular [5 + 1] cycloaddition, occurs under mild conditions, with high functional group tolerance and regioselectivity, and can be employed for late-stage functionalization. Upon heating at refluxing chlorobenzene temperature, these triazine-N-oxides undergo dinitrogen extrusion to form isoxazoles in very high yields.

The Anticancer Action of a Novel 1,2,4-Triazine Sulfonamide Derivative in Colon Cancer Cells

Cancer therapy is one of the most important challenges of modern medical and chemical sciences. Among the many methods of combating cancer, chemotherapy plays a special role. Imperfect modern chemotherapy justifies continuing the search for new, more effective, and safe drugs. Sulfonamides are the classic group of chemotherapeutic drugs with a broad spectrum of pharmacological activity. Recent literature reports show that sulfonamide derivatives have anti-tumor activity in vitro and in vivo. The aim of the study was to synthesize a novel 1,2,4-triazine sulfonamide derivative and check its anticancer potential in DLD-1 and HT-29 colon cancer cells. The biological studies included MTT assay, DNA biosynthesis, cell cycle analysis, Annexin V binding assay, ethidium bromide/acridine orange staining, and caspase-8, -9, and -3/7 activity. The concentrations of important molecules (sICAM-1, mTOR, Beclin-1, cathepsin B) involved in the pathogenesis and poor prognosis of colorectal cancer were also evaluated by ELISA. We demonstrated that the novel compound was able to induce apoptosis through intrinsic and extrinsic pathways and was capable of decreasing sICAM-1, mTOR, cathepsin B concentrations, whereas increased Beclin-1 concentration was detected in both colon cancer cell lines. The novel compound represents promising multi-targeted potential in colorectal cancer, but further in vivo examinations are needed to confirm the claim.

[1,2,4]triazines – as potential drugs in cancer chemotherapy

Cancers are a high risk for humanity. In 2018, approximately 18 million new cancer cases were diagnosed in the world. The choice of treatment depends on the type of cancer and its stage at diagnosis. The treatment of cancer consists mainly of surgical methods, radiotherapy, immunotherapy, hormone therapy and chemotherapy. Cytotoxic drugs can be used both in monotherapy and combination therapy. In 2009-2018, the US. Food and Drug Administration (FDA) approved about 356 new drugs for cancer therapy. However, it should be noted that despite the increasing availability of modern drugs, this disease is the second leading cause of death in the world. Research on the development of a cytotoxic drug is aimed at designing a compound structure, whose action is directed at cancer cells while not affecting normal cells. Triazine derivatives might be the chemical structure with potential anticancer activity. This scaffold has been used in oncological therapy since 1965. Depending on the location of the nitrogen atoms in the ring, three isomers can be distinguished: [1,2,3]triazines, [1,2,4]triazines, [1,3,5]triazines. Modification of the structure of the [1,2,4]triazine derivatives should provide stronger cytotoxic properties and reduce the side effects of the novel drug. Designing new preparations also aims to improve the patient’s quality of life. This review will briefly present how the modification of the chemical structure of [1,2,4]triazine derivatives increases their cytotoxic activity against cancer and why these compounds may be better tolerated than current therapy.

The Chemistry of Triazine Isomers: Structures, Reactions, Synthesis and Applications

Triazine is the six-membered heterocyclic ring containing three nitrogens, which replace the carbon-hydrogen unit in the benzene ring. Based on nitrogen position present in the ring system, it is categorized in three isomeric forms, i.e., 1, 2, 3-triazine (vicinal triazine), 1, 2, 4-triazine (asymmetrical triazine or isotriazine) and 1, 3, 5-triazine (symmetrical or s-triazine or cyanidine). Triazines have a weakly basic property. Their isomers have much weaker resonance energy than benzene structure, so nucleophilic substitution reactions are more preferred than electrophilic substitution reactions. Triazine isomers and their derivatives are known to play important roles possessing various activities in medicinal and agricultural fields such as anti-cancer, antiviral, fungicidal, insecticidal, bactericidal, herbicidal, antimalarial and antimicrobial agents.

Synthesis and screening of (E)-3-(2-benzylidenehydrazinyl)-5,6-diphenyl-1,2,4-triazine analogs as novel dual inhibitors of α-amylase and α-glucosidase

(E)-3-(2-Benzylidenehydrazinyl)-5,6-diphenyl-1,2,4-triazines analogs 1-27 were synthesized by multi-step reaction scheme and subjected to in vitro inhibitory screening against α-amylase and α-glucosidase enzymes. Out of these twenty-seven synthetic analogs, ten compounds 14-17, 19, and 21-25 are structurally new. All compounds exhibited good to moderate inhibitory potential in terms of IC₅₀ values ranging (IC₅₀ = 13.02 ± 0.04-46.90 ± 0.05 µM) and (IC₅₀ = 13.09 ± 0.08-46.44 ± 0.24 µM) in comparison to standard acarbose (IC₅₀ = 12.94 ± 0.27 µM and 10.95 ± 0.08 µM), for α-amylase and α-glucosidase, respectively. Structure-activity relationship indicated that analogs with halogen substitution(s) were found more active as compared to compounds bearing other substituents. Kinetic studies on most active α-amylase and α-glucosidase inhibitors 5, 7, 9, 15, 24, and 27, suggested non-competitive and competitive types of inhibition mechanism for α-amylase and α-glucosidase, respectively. Molecular docking studies predicted the good protein-ligand interaction (PLI) profile with key interactions such as arene-arene, H-<, <-<, and <-H etc., against the corresponding targets.

Anthra[1,2-d][1,2,3]triazine-4,7,12(3H)-triones as a New Class of Antistaphylococcal Agents: Synthesis and Biological Evaluation

The development and spread of resistance of human pathogenic bacteria to the action of commonly used antibacterial drugs is one of the key problems in modern medicine. One of the especially dangerous and easily developing antibiotic resistant bacterial species is Staphylococcus aureus. Anthra[1,2-d][1,2,3]triazine-4,7,12(3H)-triones 22-38 have been developed as novel effective antistaphylococcal agents. These compounds have been obtained by sequential conversion of 1-amino-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid (1) and 1-amino-4-bromo-9,10-dioxo-9,10-dihydroanthracene-2-carboxylic acid (2) into the corresponding amides 5-21, followed by subsequent endo-cyclization under the influence of sodium nitrite in acetic acid. Evaluation of the antimicrobial activity of the synthesized compounds against selected species of Gram-positive and Gram-negative bacteria as well as pathogenic yeasts of the Candida genus has been carried out by the serial dilution method. It has been established that anthra[1,2-d][1,2,3]triazine-4,7,12(3H)-triones exhibit selective antibacterial activity against Gram-positive bacteria. Eight, six and seven, out of seventeen compounds tested, effectively inhibited the growth of S. aureus ATCC 25923, S. aureus ATCC 29213 and S. epidermidis ATCC12228, respectively, at a concentration equal to 1 µg/mL or lower. The high antistaphylococcal potential of the most active compounds has been also confirmed against clinical isolates of S. aureus, including the MRSA strains. However, bacteria of the Staphylococcus genus have demonstrated apparent resistance to the novel compounds when grown as a biofilm. None of the four selected compounds 3234 and 36 at a concentration of 64 µg/mL (128 or 256 × MIC-against planktonic cells) has caused any decrease in the metabolic activity of the staphylococcal cells forming the biofilm. The kinetic time-kill assay revealed some important differences in the activity of these substances. Compound 33 is bacteriostatic, while the other three demonstrate bactericidal activity.

15N labeling and analysis of 13C–15N and 1H–15N couplings in studies of the structures and chemical transformations of nitrogen heterocycles

This review provides a generalization of effective examples of ¹⁵N labeling followed by an analysis of J_CN and J_HN couplings in solution as a tool to study the structural aspects and pathways of chemical transformations in nitrogen heterocycles.